A top 10 BYU team would likely get an at large bid. In 12 years, BYU won the MWC outright 3 times, and I think the AAC is stronger (and thus more difficult to win) than the MWC.
I like playing lots of P5 teams. If we can't win those, do we really deserve to be in the playoffs?
If a couple of other strong teams (i.e., Boise) join the AAC, then maybe. But I'd also want to wait and see what kind of movement there is among the P5 conferences, too.
I think right now BYU is in a pretty good spot, and I wouldn't jump ship to the AAC too quickly.